Combination weighers are commonly used today in the food industry to generate portions of food products fulfilling a pre-defined weight targets. Such a combination weighers comprises a dispersion unit configured to receive food items from an infeed unit typically positioned above, a plurality of conveyance units that extend radially away from the dispersion units for receiving food items from the dispersion unit, and a plurality of weighing hoppers associated to each of the conveyance units for receiving food products therefrom. The weighing hoppers are operated by a control unit by repeatedly monitoring the weight in each of the weighing hopper for finding an optimal weight combination in two or more weighing hoppers such that a minimal overweight is obtained. Subsequently the food products are dropped from the selected two or more weighing hoppers into a common area, e.g. a bag, tray or the like.
Such a conveyance units typically consist of trenches and screw feeders arranged therein for advancing food products received from the dispersion units and radially away and into the associated weighing hoppers. However, if there is some size variation in the food products, some of the larger food products may not enter the trenches because their width may be larger than the width of the trenches, and more seriously these larger food products may block the access of other food products therein. This will obviously greatly affect the throughput of the machine, and also require a manual labor to stop the blocking. The most common solution to overcoming this problem is to widen the width of the trenches, but that will be at the cost of overall size of the combination weigher.
Another common problem with such a combination weighers is that food products in the trenches can be clamped between the screw feeders and the wall of the trenches and thus be damaged and or even stop the screw feeders.